function helcor(alpha,delta,ls)

  real(selected_real_kind(10)) ::  helcor,alpha,delta,ls

! heliocentric correction in day, input angles in radians
  
  helcor = 0.9174077*sin(alpha)*cos(delta) + 0.3979486*sin(delta)
  helcor = helcor*sin(ls) + cos(ls)*cos(alpha)*cos(delta)
  helcor = -0.0057755*helcor
end function helcor









